Creating a Permanent Magnet (Material-N52) in COMSOL 6.0

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Hi!

I am new to COMSOL and trying to simulate the force experienced between two strips of N52 magnets of dimension "1.8mm x 1.8mm x 0.4mm". Six such magnets are kept stacked to each other such that two such strips face each other as shown in attached picture 1.

  1. Since the magnet feature is not available in COMSOL 6.0, I used the "Magnetic Flux Conservation" under the "Magnetic Fields, No Current (mfnc)" study to carry out my simulation.

  2. I obtained the data related to B-H curve of N52 and its coercive magnetic field from an open source software named "FEMM 4.2" which is also shown in attached picture 2.

  3. The way I have input this material data about N52 from FEMM into COMSOL is shown in screenshot picture 3. Note that "Magnetic Flux Conservation 2" has been defined for upper block of magnets and "Magnetic Flux Conservation 3" has been defined for the lower block.

  4. I intend to obtain the attractive force between the strips now. The screenshot 4 gives the result. The gap between the strips being 1.25mm. The force that is obtained is 0.32633 N. When I perform the same simulation in FEMM, the force turns out to be 0.219628 N (Screenshot 5). Question 1: I don't understand this discrepancy in the softwares, both being FEM and used extensively in industry. Is there something wrong in the way I am giving inputs to COMSOL?

Question 2: When I want to keep the magnets in a strip in a way that each adjacent magnet has oppositely aligned magnetization direction (i.e, if say a magnet has its magnetization vector (pointing from South to North) pointing in +z direction, then its adjacent magnets' magnetization vector must point in the -z direction). When I do this to both the strips, surprisingly the results turn out to be very different again and there's mismatch between both the softwares. Interestingly, COMSOL doesn't even show magnetic lines of force for the magnets which are magnetized in opposite magnetization sense, as shown in screenshot 6 (which also shows mismatch in forces again).

Can someone please help me as to what exactly is going wrong in my approach? Whether firstly, I am translating the information about N52 magnets correctly and secondly why is there a mis-match?

Thanking you in anticipation of your kind and earliest response in this regard.

Regards, Chetan.



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